A communication system is comprised, at a minimum, of a transmitter and a receiver interconnected by a communication channel. The transmitter is operative to transmit communication signals generated at, or applied to, the transmitter upon the communication channel so that the receiver can detect the transmitted signals. To transmit the communication signals upon the communication channel, the transmitter must convert the signals into a form to permit their transmission upon the communication channel.
In a two-way communication system, transmitter and receiver pairs form communication stations through which communication signals can both be transmitted and received. Because of such capability both to transmit and to receive communication signals, two-way communication can be effectuated at such a communication station.
A radio communication system is a communication system in which the communication channel is formed of a radio frequency communication channel. The radio frequency communication channel is formed of a range of frequencies of the electromagnetic frequency spectrum. The transmitter, i.e., a radio transmitter, of a radio communication system converts a communication signal generated at, or applied to, the radio transmitter into a form permitting its transmission upon the radio frequency channel. The receiver, i.e., a radio receiver, operable in a radio communication system is tuned to the radio frequency channel upon which the radio transmitter transmits the communication signal. When so-transmitted, the radio receiver can receive the transmitted signal.
Radio transceiver circuitry, formed of both radio transmitter and radio receiver portions, permit two-way communications to be effectuated. Two-way communication is effectuated between a remotely-positioned radio transceiver by communicating transmit and receive signals upon one or more radio communication channels.
A radio communication system is advantageous for the reason that fixed connections, such as wirelines or cables, are not required to form the communication channel which interconnects the radio transmitter and radio receiver. Utilization of a radio communication system is, therefore, particularly advantageous when a fixed connection interconnecting a transmitter and a receiver would be inconvenient or impractical.
By utilizing transmitters capable of generating a communication signal of high signal strength and utilizing a radio receiver of a high sensitivity, the transmitter and receiver can be separated by a significant separation distance while still permitting adequate communication of the transmitted signal by the radio transmitter to the radio receiver.
A cellular communication system is exemplary of a radio communication system. Cellular communication networks which form the infrastructure of cellular communication systems have been installed throughout significant portions of the world and large numbers of subscribers to such cellular networks are able to communicate telephonically when positioned in areas encompassed by such cellular networks.
Utilization of a cellular communication system is advantageous as a user can communicate pursuant to the communication system by way of a radiotelephonic device, i.e., "cellular phone" or "subscriber unit", positioned anywhere throughout the geographical area encompassed by the network. As wireline connections are not required to effectuate communication, telephonic communication can be effectuated by a user, e.g., when traveling in a motor vehicle or in other situations in which communication by way of a communication system requiring the use of a fixed connection between the transmitter and receiver would be inconvenient or impractical.
Other types of wireless communication systems similarly are advantageously utilized as fixed connections between a radio transmitter and radio receiver are not required to effectuate communication therebetween. Transceivers analogous to the radiotelephonic devices utilized in a cellular communication system are similarly utilized to effectuate communications in other types of radio communication systems.
Advancements in communication technologies have permitted the portability of the radiotelephonic devices utilized in such radio communication systems to be increased. As electrical circuitry becomes increasingly miniaturized, the volumetric requirements of electronic devices including such circuitry are permitted to be reduced.
Radiotelephonic devices are exemplary of electronic devices which have been constructed to be of increasingly smaller sizes and weights. Commercially-available radiotelephonic devices operable in various cellular communication systems are now of weights of only several ounces and are of dimensions of only a few cubic inches. A radiotelephonic device conventionally includes a speaker to permit a user of the device to listen to signals transmitted to the device and a microphone to receive voice, or other, signals generated by the user. A housing is used to support the circuitry of the radiotelephonic device, including the speaker and microphone. The speaker and microphone are typically supported at opposite side portions of the housing to permit concurrent positioning of the speaker proximate to the user's ear and the microphone proximate to the user's mouth. When the radiotelephonic device is operated the user is able to concurrently listen to signals generated at the speaker and to speak into the microphone.
A speaker is a transducer which coverts electrical energy into mechanical energy, and a microphone is a transducer which converts mechanical (e.g., aural) energy into electrical energy. A microphone typically includes a diaphragm which vibrates upon the application of aural energy thereto. In some microphones, an electrical winding is positioned proximate to the diaphragm and vibrations of the diaphragm induce currents in the winding. Other microphones are formed of electrets which include an electret membrane and an electrical circuit coupled thereto. As a result of the aforementioned circuit miniaturization, the circuitry of a radiotelephonic device can now be housed within a housing of much-reduced lengthwise dimensions. The circuitry of the radiotelephonic device can be housed in a housing of lengthwise dimensions which, when the speaker supported at one end side of the housing is positioned proximate to the user's ear, the microphone supported at an opposing end side of the housing cannot be positioned immediately proximate to the user's mouth.
By selecting a microphone of appropriate "pick-up" characteristics, the microphone is still able to detect adequately the voice signal generated by the user. However, when the microphone is not positioned immediately proximate to the user's mouth, additional amounts of background noise are also detected by the microphone.
The background noise together with the voice signal are modulated by circuitry of the radiotelephone and then transmitted. Such background noise reduces the quality of the signal communicated by the radiotelephone. That is to say, the signal-to-noise ratio of the transmitted signal is reduced as the noise component becomes a relatively larger portion of the signal transmitted by the radiotelephone. With additional reductions in the lengthwise dimensions of the radiotelephone and resultant positioning of the microphone farther away from the user's mouth, the problems associated with background noise become more significant.
Some constructions of radiotelephones include a flip portion which is rotatably coupled to a main housing portion of the radiotelephonic device. The flip portion can be rotated into an open position to form an extension extending beyond an end portion of the main housing portion. A microphone positioned at the flip portion of the radiotelephonic device can be positioned closer to the user's mouth than when positioned at the main housing portion. By positioning the microphone at the flip portion, such that the microphone can be positioned closer to the user's mouth, the signal-to-noise ratio of a voice signal generated by the user relative to background noise can be increased, thereby facilitating communications of improved quality.
Some other constructions of radiotelephones include a slidable arm which is slidably coupled to a main housing portion of the radiotelephonic device. Such a slidable arm is operable in manners analogous to that of the rotatable flip portion to position a microphone closer to the user's mouth.
Positioning of the microphone at the flip portion or upon a slidable arm, however, requires electrical leads to couple the microphone with the transmitter circuitry of the radiotelephonic device to extend through a rotatable coupling which rotatably couples the flip portion to the main housing portion. After repeated rotation of the flip portion, such leads are susceptible to breakage. More elaborate connectors can be utilized, such as a swivel connector to interconnect the microphone and the transmitter circuitry of the radiotelephonic device, but such connectors are relatively costly. Additionally, such connectors are sometimes also susceptible to radio frequency interference which sometimes results in "motorboating" sounds, and rubbing together of such connectors can also result in the generation of electrical noise. Such sounds also degrade the quality of communications effectuated pursuant to the radiotelephonic device.
In some other constructions of radiotelephonic devices, a flip portion is also utilized, but the microphone is mounted within the main housing portion of the radiotelephonic device. In such constructions, the flip or slidable arm portion, used primarily for aesthetic reasons, also serves, to some extent, to reflect voice signals generated by the user towards the microphone.
As the physical dimensions of radiotelephonic devices continue to decrease, it shall likely become increasingly difficult to limit pick-up of background noise if the microphone must be positioned increasingly farther away from the user's mouth. What is needed, therefore, is a manner by which to permit positioning of a microphone close to the user's mouth without requiring electrical leads to extend to the diaphragm.
It is in light of this background information related to transducer circuitry, such as that used in radiotelephonic devices, that the significant improvements of the present invention have evolved.